Gamma-Ray-Induced\nSynthesis of Sugars in Meteorite\nParent Bodies

Sugars play an indispensable role for all living organisms.\nGiven\nthat certain sugars have been identified in carbonaceous chondrites,\nthese compounds might have been delivered to the early Earth via meteorites.\nThe genesis of these sugars, however, has been a subject of debate;\nthey are considered to have either originated from UV irradiation\nof interstellar ice or from hydrothermal reactions within the environments\nof meteorite parent bodies. The parent bodies of carbonaceous chondrites\ncontained water ice which underwent hydrothermal alteration as a result\nof the internal warming of these bodies. The most likely source of\nthis heat is believed to be the decay of radioactive nuclides, such\nas <sup>26</sup>Al. In our previous research, we demonstrated that\ngamma-ray exposure significantly enhances the synthesis of amino acids\nfrom aqueous solutions of formaldehyde, ammonia, and methanol. Nonetheless,\nthe impact of radiation on sugar formation has not been investigated.\nHence, the current study is conducted with a focus on the formation\nof aldose sugars through gamma-ray irradiation to such solution mixtures.\nOur results reveal that gamma-rays indeed promote the formation of\nsugars, including ribose, without the presence of a catalyst such\nas glycolaldehyde. Furthermore, we demonstrated that the presence\nof ammonia enhanced the yield of aldose sugars, although higher concentration\nof ammonia inhibited sugar production. Our findings suggest that gamma-rays\nfrom the decay of <sup>26</sup>Al played a significant role in the\nformation of sugars during low-temperature aqueous alteration inside\nmeteorite parent bodies.